1. Field of the Invention
The present invention relates to robot end effectors and more particularly to a gripper tool and changer which provide straight line motion.
2. Description of the Related Art
The most common robot end effector is the gripper used for pick-and-place operations. To minimize cost, pivoting links are used to produce either ordinary angular motion (as with pliers) or parallelogram motion in which the gripper faces remain parallel but move through an arc. For about a 50% higher price, a straight line sliding gripper is widely available that, besides adding the obvious advantage of gripping with parallel faces, also improves the accuracy of pick-and-place operations and, furthermore, simplifies robot programming by deleting the arc component of gripper travel. In addition to higher cost, however, the sliding gripper is also penalized by substantially higher friction.
There is a need to reduce the cost of straight line robot grippers. As will be disclosed below, the present invention offers an opportunity for such cost reduction.
A further problem related to robot grippers is seen in the methods currently used to change from one gripper type to another. This capability is a major element of the robot market, since tool change is clearly preferred over additional robots. Also, tool changes require down time and, therefore, should be done quickly. Current methods range from manual (slow) to automatic. A significant problem with these methods is that most gripper tools contain their own dedicated actuator, easily the most costly element. The current approach to straight line grippers usually requires one or two actuators, plus synchronizing means for the equal and opposite motions.
There is a need to simplify the present approach to automatic robot tool changing, particularly by use of a passive tool that would eliminate the need for dedicated actuators.